9/2/2020

LECTURE NO. 16
ACOUSTICS OF A
BUILDING

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CONTENTS:

Characteristics of Sound

Acoustic defects

Requirement of good Acoustic

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INTERODUCTION:
Sound is a vibration in an elastic medium such
as air, water, building materials and earth.
It is generated by vibrated bodies in the form
of waves of compression and rarefaction in
the air.
A full circuit by a displaced particle is called a
cycles.
The time required for one complete cycle is
called period.
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INTERODUCTION:
The number of complete cycles per second is
the frequency(Pitch) of vibration.(hertz)

Frequency= Speed of sound

Wavelength

The range of human hearing is very wide

extending from 20 Hz to 20,000 Hz(or 20
kHz)
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INTERODUCTION:
Wavelength of Sound:

It is the distance a sound wave traveling during

one cycle of vibration or wavelength is the
distance between adjacent regions where
identical conditions of particle displacement
occur.

Wavelength (ft) = Speed of sound (ft/sec)

Frequency (hertz)
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INTERODUCTION:
The speed of sound in air is about 1,130 feet
per second (770 miles per hour) at normal
temperature and pressure.

Characteristics of Sound

Loudness: The human perception of how

much energy a sound wave carries

determined mainly by the amplitude of the

sound wave

Decibel (dB)- unit used to measure sound

intensity or loudness.
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Characteristics of Sound

I=

Where I = sound intensity (w/m2

W = sound power (Watt)
d = distance form sound source
(m)

Characteristics of Sound

Loudness of Sound in Decibels

Sound Loudness Hearing
(dbs) Damage
Average 40-50
Home
Loud Music 90-100 After long
exposure
Rock 115-120 Progressive
Concert
Jet Engine 120-170 Pain
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Characteristics of Sound

Threshold of hearing
-sound of the quietest sound that can be heard
under ideal conditions is 0 dB.

Threshold of Pain
- Sound level of 120 dB which can pain and
damage to the ears.

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ACOUSTICS:
Acoustics is the interdisciplinary science that
deals with the study of all mechanical
waves in gases, liquids, and solids
including vibration,sound, ultrasound and in
frasound. A scientist who works in the field
of acoustics is an acoustician while someone
working in the field of acoustics technology
may be called an acoustical engineer. The
application of acoustics is present in almost
all aspects of modern society with the most
obvious being the audio and noise
control industries. 12

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ACOUSTICS:
The word "acoustic" is derived from
the Greek word ἀκουστικός (akoustikos),
meaning "of or for hearing, ready to
hear" and that from ἀκουστός (akoustos),
"heard, audible",which in turn derives from
the verb ἀκούω (akouo), "I hear".

The study of acoustics revolves around the

generation, propagation and reception of
mechanical waves and vibrations.

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TYPES OF MATERIALS:
SOUND ABSORBERS

SOUND DIFFUSERS

NOISE BARRIERS

SOUND REFLECTORS

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TYPES OF MATERIALS:

SOUND ABSORBERS
These sound absorbing acoustical panels and
soundproofing materials are used to eliminate
sound reflections to improve speech intelligibility,
reduce standing waves.

Typical materials are open cell polyurethane foam,

cellular melamine, fiberglass, fluffy fabrics and other
porous materials. A wide variety of materials can be
applied to walls and ceilings depending on your
application and environment.
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SOUND ABSORBERS

TYPES OF MATERIALS:
These materials vary in thickness and in shape to
achieve different absorption ratings depending on
the specific sound requirements.

TYPES –
❑Acoustical foam panels
❑White paintable acoustical wall panels
❑Fabric wrapped panels
❑Acoustical wall coverings
❑Ceiling tiles
❑Baffles and banners for ceiling
❑Fibre glass blankets and roll 17

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SOUND ABSORBERS
TYPES OF MATERIALS:

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Available Sizes:
24" x 24" (nominal)
Specify grid when
ordering:
9/16 or 15/16

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SOUND DIFFUSERS

◦ These devices reduce the intensity of sound by scattering it over an

expanded area, rather than eliminating the sound reflections as an
absorber would. Traditional spatial diffusers, such as the polycylindrical
(barrel) shapes also double as low frequency traps. Temporal diffusers,
such as binary arrays and quadratics, scatter sound in a manner similar
to diffraction of light, where the timing of reflections from an uneven
surface of varying depths causes interference which spreads the sound.
◦ This diffuser generates a uniform polar response over a broad
frequency range using a pre-rotated pyramidal pattern to create 16
angles of reflection.

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PYRAMIDAL DIFFUSER
QUADRA PYRAMID DIFFUSER

•This traditional industry workhorse disperses sound uniformly over a broad frequency
range. A quick solution to reduce flutter echo.

DOUBLE DUTY DIFFUSER QUADRATIC DIFFUSER

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NOISE BARRIERS

◦ These materials range from dense materials to block the transmission of

airborne sound to devices and compounds used to isolate structures
from one another and reduce impact noise.

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BARRIERS COMPOSITES
•Sound barrier materials are •Composite materials are manufactured
used to reduce the transmission from combinations of various materials
of airborne sound. The from open and closed celled foams to
BlockAid® series of products quilted fiberglass and barrier. These
include the standard one pound products are used to block and absorb
per square foot non reinforced sound for machine enclosures as well
barrier, transparent material as blocking airborne sound and impact
when observation or supervision noise. Some of these products include
is required, reinforced vinyl to Composite Foams, StratiQuilt Blankets
create a hanging barrier and Floor Underlayment.
partition.

VIBRATION CONTROL
•Vibration control products are used to absorb vibration energy and
prevent structural noise transmission. These include vibration
damping compounds and vibration pads, isolation hangers, and
resilient clips. They improve sound transmission loss.

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FABRICS

• Acoustical fabrics are typically used to either absorb sound or as a cover for
acoustical panels. Some fabrics can also be used as a speaker grill cloth or as a
finish on other types of materials.

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SOUND CHANNELS WALL FABRICS GUILFORD OF MAINE

•Acoustical wall fabric is a dimensional fabric •Guilford of Maine® Fabric is and
that offers excellent acoustical properties, acoustically transparent fabric used to
unmatched fade resistance, and a fire/smoke cover many of our products including
retardant class A rating. Sound channels® is acoustical wall panels, diffusers, and
resistant to moisture, mildew, rot, bacteria, corner traps. Fabric is also sold
and is non-allergenic. Produced with no separately as speaker grill cloth, wall
voc’s (volatile organic compounds), ods’s covering and for other field
(ozone depleting substances), heavy metals applications.
or formaldehyde, it's the perfect acoustic
fabric for offices, classrooms, conference
centers or any area where speech intelligibility
is a critical factor.

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THANK YOU !!

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